Monash scientists find ‘bad guy’ blood cells vital to gut health

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A Monash University collaboration has found that eosinophils, a type of white blood cell commonly associated with asthma and allergy, play an important role in maintaining a healthy gut.

Professor Nicola Harris from Monash’s Central Clinical School made the discovery working with study co-lead Professor Kathy McCoy from the University of Calgary and scientists from Switzerland.

Their paper was published in Immunity.

“The study showed a critical role for eosinophils in facilitating mutualistic interactions between host and microbiota, the millions of bacteria in the gut,” said Professor Harris.

“It turns our views of eosinophil function on its head and will no doubt spur a lot more research into these relatively rare cells,” she said.

Eosinophils make up about 1-2 per cent of circulating white blood cells in healthy people in developed countries but are present in increased numbers in people who are severely allergic.

“They play a tissue-destructive, pathological role in these allergies, they’re the bad guys,” said Professor Harris.

Professor Harris continued. “We set out to answer why these supposedly tissue-destructive cells were sitting in the gut.”

The scientists investigated the possible role of eosinophils in the main functions of the small intestine using germ-free animal models and advanced 3-D microscopy. They found that eosinophils co-ordinated the gut’s response to bacteria. 

“They were limiting overt inflammation and by doing that they were limiting tissue damage,” said Professor Harris.

“The most important factor of this damage is the length of the villi, the finger-like projections that come up from the wall of the intestine, which absorb nutrients.

“We found eosinophils kept those villi intact and without them the villi became much shorter and lipid uptake was reduced.

“So, they were helping to maintain this absorptive area that allowed extraction of nutrients from the diet at a proper level.”